Following the rapid development of various 3C products, the performances of all kinds of electronic components of the 3C products have been rapidly promoted to have faster and faster processing speed. The electronic components work at high speed and generate high heat at the same time. The heat must be efficiently dissipated outward. Otherwise, the temperature will rise very quickly to cause burnout of the electronic components. In order to avoid damage of the electronic components, in general, at least one heat dissipation unit (such as a radiating fin assembly or a heat sink) and a cooperative cooling fan are provided to dissipate the heat generated by the electronic components and thus prolong the lifetime thereof.
Please refer to FIG. 1, which is a perspective exploded view of a conventional fan device 8. The fan device 8 includes at least one fan propeller 81, at least one stator assembly 82, at least one bearing 83 and a shaft seat 84. The bearing 83 has a shaft hole 831. The shaft seat 84 has a bushing 841 for receiving the bearing 83 therein. The fan propeller 81 has a shaft 811 and multiple blades 812. The shaft 811 is inserted in the shaft hole 831 of the bearing 83. The stator assembly 82 has a silicon steel sheet assembly 821 and at least one substrate board 822. The substrate board 822 is connected to one side of the silicon steel sheet assembly 821. Multiple control circuits are arranged on the substrate board 822. The stator assembly 82 is press-fitted around the bushing 841 of the shaft seat 84. Therefore, the silicon steel sheet assembly 821 of the stator assembly 82 must be formed with a central perforation 8211 and the substrate board 822 must be also formed with a central perforation 8221. By means of the perforations 8211, 8221, the stator assembly 82 can be securely fitted around the bushing 841 and coupled with the shaft seat 84. However, the multiple control circuits arranged on the substrate board 822 must avoid the perforation 8221 of the substrate board 822. As a result, the space for the layout of the control circuits is limited and it is hard to deploy the control circuits of the fan device. Moreover, a large amount of material of the substrate board is wasted. According to the aforesaid, the conventional fan device has the following defects:    1. It is hard to deploy the circuits.    2. The space for the layout of the circuits is limited.    3. A large amount of material is wasted.